Height adjustment mechanism for a back rest or an arm rest of a chair

Abstract

A chair has a mechanism for adjusting height of a component, i.e. a back rest or an arm rest of the chair. The mechanism comprises a vertically extending rail, a rail grip and a rotatable control member having an orbital portion which orbits about the axis of rotation of the control member. The control member rotates to orbit the orbital portion between a release position where the rail and rail grip are slideable relative to one another to adjust the height of the chair component and a locking position where the orbital portion of the control member pushes the rail and rail grip into locking engagement with one another preventing height adjustment of the chair component.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
       1. A chair having a mechanism for adjusting height of a component of the chair, said mechanism comprising a vertically extending rail, a rail grip and a rotatable control member, said control member being provided with an orbital portion which upon rotation of said control member orbits between a release position where said rail and said rail grip are slideable relative to one another to adjust the height of the chair component and a locking position where said orbital portion pushes said rail and said rail grip into engagement with one another to lock the chair component against adjustment, wherein said orbital portion of said control member engages said rail when in the locking position, said rail having a ribbed surface for holding said orbital portion of said control member in a fixed position on said rail. 
     
     
       2. A chair having a mechanism for adjusting height of a component of the chair, said mechanism comprising a vertically extending rail, a rail collar sleeved over said rail, a rail grip and a rotatable control member, said control member being provided with an orbital portion which upon rotation of said control member orbits between a release position where said rail and said rail grip are slideable relative to one another to adjust the height of the chair component and a locking position where said orbital portion pushes said rail and said rail grip into engagement with one another to lock the chair component against adjustment, said rail collar being aligned with said rail when said control member is in the release position and being tilted relative to and binding on said rail when said control member is in the locking position. 
     
     
       3. A chair as claimed in claim 2 wherein said control member is located in a vertically spaced relationship to said rail collar sleeve. 
     
     
       4. A chair as claimed in claim 2, wherein said control member comprises a pair of axially aligned axle portions rotatably held by said collar and separated by said orbital portion which is axially offset from said axle portions. 
     
     
       5. A chair as claimed in claim 4 wherein said control member is located in a vertically spaced relationship to said rail collar sleeve. 
     
     
       6. A chair as claimed in claim 2, wherein said rail collar has opposite side surfaces both of which bind on said rail when said mechanism is in the locking position. 
     
     
       7. A chair as claimed in claim 6 wherein said control member is located in a vertically spaced relationship to said rail collar sleeve.